The present invention relates to a self-drilling fastener, comprising a fastener element with a slot, formed at its free end and constructed parallel to the axis of the fastener, and a platelet-shaped drilling insert, the end of which is inserted into the slot at the fastening element, the drilling insert being connected positively and non-positively due to the deformation of the jaws forming the boundary of the slot at the fastening element.
A self-drilling screw is already known (DE-C-28 01 962), the drilling part of which is formed by a cutting insert inserted into a longitudinal slot of the screw shaft. The side edges of the cutting insert are provided with recesses, into which the edge region or partial region in question of the jaws of the screw shaft, forming the boundary of the slot, is or are pressed in order to form a solid positive and non-positive connection between the cutting insert and the screw shaft. The corresponding regions of the jaws are thus pressed into indentations at the surface of the platelet-shaped cutting insert until they lie against the base of this recess. There is thus only a slight deformation of the edge regions of the jaws and no particularly strong plastic deformation of the jaws due to the solid counter-surface at the cutting insert. Many years of practical use have shown that this type of fastening of the cutting insert has been entirely optimum in the past and that the required safety against loss is provided by this positive and non-positive holding of the cutting insert. Furthermore, the necessary torque during the drilling can be transferred properly.
As a result of the optimum use of such self-drilling screws with a platelet-shaped cutting insert, the range of uses is constantly being enlarged. The drilling is not restricted only to thin sheet metal. This means that the depths of drilling, which can be managed by such self-drilling fasteners, are also constantly being extended. In order to be able to use such self-drilling fasteners also in thick material that is, for example, in steel girders with a wall thickness of 8 mm, 12 mm or more, it is necessary to make the steel inserts correspondingly longer.